Heated Steering Wheel (Diagnostics & Symptom Tests): Other Lexus GS IV

PRECAUTION [03/2012 - ]

1. HANDLING PRECAUTIONS FOR SRS AIRBAG SYSTEM This vehicle is equipped with a Supplemental Restraint System (SRS). Failure to carry out service operations in the correct sequence could cause the SRS to unexpectedly deploy during servicing. This may cause a serious accident. Before servicing (including inspection, replacement, removal and installation of parts), be sure to read the precautionary notices for Supplemental Restraint System. Refer to «PRECAUTION [03/2012 - ]»(ref-600414-S28838177152014022400000) .

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1. SYSTEM DIAGRAM

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1. HEATED STEERING WHEEL SYSTEM The heated steering wheel heats the steering wheel when the steering heater switch is operated. The heated steering wheel uses a thermistor inside of the steering wheel to detect the heater temperature and maintain the set temperature. The heated steering wheel timer function turns off the heater after a predetermined period of time.
2. HEATER CONTROLLER SYSTEM Operation description When the power switch is on (IG), pressing the steering wheel controller momentary switch on the steering heater switch illuminates the LED and current is output from the steering controller to the heater of the heated steering wheel. Pressing the momentary switch again turns off the LED and stops the current from being output. A thermostat is installed in the steering wheel as a safety mechanism. The heated steering wheel switch LED will blink at 0.3 second intervals when either of the following occurs: 1) an open or short in the steering wheel thermistor continues for 2 seconds or more; or 2) the steering heater switch momentary switch is pressed continuously for 10 seconds or more. If the normal condition is restored for 2 seconds or more, the previous operation before the malfunction occurred continues. However, regardless of if a malfunction is detected and the malfunction operation is occurring, and regardless of if the normal condition is restored and the system is operating normally, the timer will turn off the heater 30 minutes after the switch was first turned on. Signal input / output description Signal Signal Name Function Signal Type Input Thermistor input Input of voltage corresponding to heater temperature Analog input Input Temperature setting input Input of voltage corresponding to temperature setting Analog input Input Operating switch input Input of power circuit latch operation estimate signal LOW / HI input Output LED output Output of LED LOW / HI input Output Heater output Output of heater LOW / HI input Output Latch output Power circuit maintenance LOW / HI input Safety function Content Operation When thermistor trouble is detected Heater off When overheating (175°C (347°F)) of controller is detected Heater off When load short current (50 A or more) is detected Heater off When undervoltage (4.5 V) is detected Heater off OFF timer (30 min.) After preset time of timer passes, heater off Reverse voltage protection Protection circuit operates

FAIL-SAFE CHART [03/2012 - ]

1. MALFUNCTION DETECTION Operation when malfunction is detected Content Operation When thermistor trouble is detected Heater off When overheating (175°C (347°F)) of controller is detected Heater off When load short current (50 A or more) is detected Heater off When undervoltage (4.5 V) is detected Heater off OFF timer (30 min.) After preset time of timer passes, heater off Reverse voltage protection Protection circuit operates Malfunction detection conditions When an open or short in the steering wheel thermistor continues for 2 seconds or more. When the steering heater switch momentary switch is pressed continuously for 10 seconds or more. Malfunction display The LED of the steering heater switch blinks at 0.3 second intervals. Restore condition If the normal condition is restored for 2 seconds or more, the previous operation before the malfunction occurred continues. However, regardless of if a malfunction is detected and the malfunction operation is occurring, and regardless of if the normal condition is restored and the system is operating normally, the timer will turn off the heater 30 minutes after the switch was first turned on.